Method for the uniform extrusion coating of welding flux compositions

ABSTRACT

A method and apparatus are provided for the uniform extrusion coating of flux mixtures on welding rod or wire, in which a sonic or ultrasonic wave vibration at a frequency from about 5,000 to about 400,000 c.p.s. is applied to the flux mixture to maintain its uniformity, and thereby prevent the obstruction to the smooth extrusion coating of the welding flux mixture as the flux mixture is fed under pressure to the extrusion nozzle.

United States 2 Patent Yasuo Torigai Funabashi-shi;

Keizo Ishizaki, Tokyo, both of Japan [21 Appl. No. 830,332

[72] Inventors Continuation-impart of application Ser. No. 656,969, May22, 1967, now Patent No. 3,456,295. Continuation of application Ser. No.337,644, Jan. 15, 1964,

now abandoned.

[54] METHOD FOR THE UNIFORM EXTRUSION COATING OF WELDING FLUXCOMPOSITIONS 8 Claims, 4 Drawing Figs.

52 u.s.c1 264/23, 264/174,18/13,117/202 511 1111.01 B06b3/00, B294 3 1050 FieldoiSearch 264/174,

23,176 F, 169; 18/13; l 17/202-207, DIG. 8

[56] References Cited UNITED STATES PATENTS 2,009,240 7/1935 Roberts etal 219/8 2,408,627 10/1946 Green 264/69 2,738,173 3/1956 Massa... 259/22,802,237 8/1957 Davis.... 264/169 2,843,876 7/1958 Rubli 18/13 M3,042,481 7/ 1 962 Coggesha1l.. 264/176 F 3,071,809 l/l963 Lerch 18/133,456,295 7/1969 Torigai et a1 18/13 D 3,461,942 8/1969 Hoffman et a1.264/23 FOREIGN PATENTS 135,344 1 1/1949 Australia 264/23 749,779 5/1956Great Britain... 264/23 891,295 3/1962 Great Britain l 17/D1G. 8

Primary Examiner lay H. Woo Anorney.lanes & Chapman 7 to the fluxmixture to maintain its uniformity, and thereby prevent the obstructionto the smooth extrusion coating of the welding flux mixture as the fluxmixture is fed under pressure to the extrusion nozzle.

PAIENTEUNnv 9m 3619.429

Extrusion time (min.)

Extrusion pressure m Extrusion time (min.)

METHOD FOR THE UNIFORM EX'IRUSION COATING OF WELDING FLUX COMPOSITIONSThis application is a continuation-in-part and a division of copendingU.S. Pat. application Ser. No. 656,969, filed May 22, 1967, now U.S.Pat. No. 3,456,295 issued July 22, 1969, which is a division of U.S.application Ser. No. 552,655, filed Mar. 29, 1966, and now abandoned,which is a continuation of Ser. No. 337,644, filed Jan. 15, 1964, andnow abandoned.

It has heretofore been conventional in the manufacture of flux-coatedarc welding electrodes or flux-coated wire to pro vide a rod or wire cutto a desired length, and pass this rod or wire through a coating machinevia guide members. The coating is accomplished by extruding a mass offlux mixture under pressure onto the rod or wire by means of a nozzle,which coats the rod or wire with flux composition to a predeterminedoutside diameter. An extrusion apparatus of this type is shown in U.S.Pat. No. 2,198,085 to LeToumeau et al. The operation of suchconventional devices has, however, encountered difficulty, due to thefact that the flux mixture is not a viscous fluid which can be readilyextruded and coated uniformly upon the weld rod. Therefore, the qualityof the product and the production rate of the apparatus are often verypoor. Since the problems associated with extrusion coating are affectedby complicated factors, it has been very difficult, though notimpossible, to improve the quality and production rate of the operation.Attempts have been made to vary the composition of the flux mixtureused. It has also been proposed, as mechanical countermeasures, to raisethe extrusion pressures which are applied to the flux mixture, to alignthe direction of extrusion with the axis of the rod or wire, and toimprove the configuration of the extrusion nozzle, so that the fluxpassing therethrough may have lower frictional resistance, etc. Theseattempts, however, could not attain satisfactory results.

The welding flux used for arc welding electrodes is formed by thoroughlymixing components of the flux, such as silica sand, lime, ilmenite, ironoxide, titanium, ferromanganese, or the like or organic substances infinely divided form, in particles of the order of 100 mesh. Thesecomponents are combined by kneading with a binder or an aqueous solutionof sodium silicate or potassium silicate, the mixture thereof or thelike, in order to obtain a relatively fluid mixture. The flux mixture,therefore, is similar to a mixture of water and sand, except whenorganic substances are used in large amounts.

Rheological studies made on mixtures of this type have shown that underthe influence of external force, as during extrusion, such mixtures havea tendency to exhibit what has been called dilatancy. Dilatancy is aphenomenon whereby a uniform mixture of relatively large size particlesand a liquid tends to expand in volume, due to the expansion or dilationof the particles, when abruptly subjected to a strong external pressure.The interstices between the particles increase in size and becomecapillaries, which absorb the liquid from the outer portions. Thesurface of the compressed mixture becomes dry, and its mobility isdecreased by an increase in friction between the dry particles. Asdilatancy increases, the fluidity of the mixture further decreases, andsolidification eventually takes place.

In order to provide for the movement of the flux mixture, and toeffectively extrude the flux mixture in a continuous and unifonn coatingon weld wire or red, the extrusion pressure must be capable of shearingthe bonds created by the attractive forces between the particles, andovercoming the friction between adjacent particles. When a flux mixtureof closely packed particles is subjected to pressure within an extrusioncylinder, the mixture is compressed, and contracts slightly during theinitial stage of shearing, but dilation gradually occurs as theoperation progresses. As the volume of the mixture expands, due todilatancy, the liquid binder present in the circumferential portion ofthe cylinder is drawn into the central portion of the cylinder by thecapillary action of the interstices between the particles. The centralportion of the flux mixture becomes saturated, and is squeezed out in athickened state through the nozzle, under the influence of the extrusionpressure. This portion of the mixture contains too high a proportion ofliquid, and does not effectively nor uniformly coat the weld wire orrod. On the other hand, the shortage of liquid at the wall of thecylinder and at the extrusion nozzle decreases the fluidity of themixture in that area and eventually results in its partialsolidification and adherence to the wall. As a result of the dilatancyphenomenon and the squeezing out of the liquid-rich central portion, therequired extrusion pressure increases, and the extrusion operationeventually becomes impossible. Even if the above conditions do notappear, the viscosity of the flux mixture will usually increase duringcoating, and the welding electrode obtained will show eccentricity, orthe flux coating when dry will be extremely brittle. These are the mainfactors which cause low productivity, and poor quality.

In accordance with the instant invention, the dilatancy phenomenon, thesqueezing out of the liquid-rich portion of the flux mixture, andeccentricity of the flux coating upon the welding electrode aresubstantially eliminated by applying sonic and/or ultrasonic vibrationto the particles of the flux, during extrusion, in proximity to thenonle, while applying extrusion pressures. In particular, sonic and/orultrasonic wave vibrations are provided, within the range ofapproximately 5,000 to 400,000 c.p.s., to impart sufiicient agitation toallow a continuous and uniform coating of the flux mixture underextrusion pressure. It has been found that such vibration impartsturbulent energy to the flux particles, which prevents dilatancy and theeventual squeeze out of a saturated portion of the flux mixture bymaintaining a uniform dispersion of particles within the mixture. Theuniformity of the mixture also reduces the internal friction between theparticles, thus lowering the shear resistance of the mixture andobviating increases in extrusion pressure.

The utilization of vibration in a general way to improve flow conditionsin extrusion and other pressure-flow devices is not new. However, suchvibration techniques have not been applied to the extrusion of mixturestending to undergo dilatancy, such as flux mixtures for the coatingwelding electrodes, nor can vibrations imparted by these deviceseffectively prevent dilatancy and squeezing out unless they are directedto the flux mixtures in accordance with the process of the instantinvention.

Massa, in U.S. Pat. No. 2,738,173, discloses a device for the reductionof friction between a fluid and the walls of a conduit through which itis passing, by applying high-frequency vibrations to the walls of theconduit. The vibrational waves break down a fluid film of variablethickness that tends to build up in the passage, reduce thecross-sectional area and thereby restrict the flow. The Massa device isdirected toward improving the flow of viscous liquids, such as paint, bypreventing clogging of relatively small orifices, such as spray nozzles,rather than the extrusion of mixtures containing solid particlessuspended within a liquid binder. The drive pressure necessary to spraya viscous liquid through the nozzle is much lower than that required toextrude a mixture of suspended solid particles. Furthermore, thesuspended particles in a welding flux mixture are relatively large insize, a factor which leads to particle jams and by itself could preventextrusion through a small nozzle. Simply vibrating the flow nozzlebeyond the point of cross-sectional area reduction, as shown by Massa,or at any other point, would not prevent the flux particles from beingretained within the nozzle. Assuming that the nozzle is sufficientlylarge to permit extrusion of welding flux, the vibration means shown byMassa would also not prevent dilatancy. To effectively impart turbulentenergy to the particles of welding flux mixture to prevent dilatancy,the vibration must be applied to the mixture over a relatively largearea, prior to the reduction in cross-sectional flow area within theextrusion nozzle, since the initial stages of dilatancy and squeeze outcan and do occur before the flux mixture is severely compressed.Vibrating the nozzle after the flux mixture is fully compressed as inthe Massa device would not correct the situation, where the mixture isalready dilated and partially solidified.

A method and apparatus for extruding plastic insulation covering forwiring are disclosed by Lerch in U.S. Pat. No. 3,07 l ,809. It had beenfound that extreme shear stress created during the extrusion of moltenplastic material causes tears or fractures in the extruded plastic atthe entrance of the extrusion die. Lerch prevents critical shear stressfrom being reached by varying the annular flow area for the plasticdirectly upstream of the extrusion die, at a frequency of approximatelyl0,000 c.p.s. This is accomplished by the higfrequency reciprocation ofa core tube having a conical end, within the matching conical entranceto the extrusion die. The high-frequency variation in the annular areamaintains uniformity of the plastic coating material, and prevents itsfracture upon extrusion. The use of this method and apparatus for theextrusion coating of weld wire or rod with a flux mixture, however,would not be very effective. This device would not prevent dilatancy,but to the contrary would increase the probability of its occurrence. Asdiscussed above, dilatancy occurs when a flux mixture is abruptly orsuddenly subjected to pressure. By reducing the flow area for aparticular fluid while maintaining the flow rate, the fluid isnecessarily subjected to an increase in pressure. Therefore, thesuccessive high-frequency variation of the annular flow space adjacentthe extrusion nozzle would increase the pressure upon the flux mixture,and thereby increase the tendency for the mixture to dilate. While it istrue that vibrating the flux mixture by imparting turbulent energy tothe individual particles will effectively prevent dilation, the energymust be imparted to the particles without substantially increasing thepressure upon the mixture, above that provided by the extrusioncylinder. The Lerch method and apparatus do not accomplish this, andtheir use, therefore, would be adverse to the extrusion coating of aflux mixture upon weld wire or rod.

Similarly, Russian Pat. No. 143,071 discloses for a device for theextrusion coating of wire with rubber or plastic insulating material.The wire is fed through an electromagnetic coil which imparts reciprocalmovement to an adjacent mandrel which guides the wire to the extrusionnozzle. The oscillating mandrel redistributes the pressure on theplastic material prior to its extrusion to ensure uniform coating. Sincethe means for vibrating the plastic is the mandrel which supports thewire, it necessarily follows that the wire to be coated is alsosubjected to vibrational movement. A liquefied plastic or rubber is aviscous fluid, and is sufficiently flexible to permit coating of avibrating wire. However, it does not follow that such a deviceeffectively and unifonnly extrudes and coats a welding flux material ofsuspended solid particles on wire. Unlike a viscous fluid, the vibratingwelding flux material will not adhere readily to a vibrating wire orrod. The particles will tend to break loose, thereby resulting in adiscontinuous or nonuniform flux coating. Therefore, the devicedisclosed in the Russian patent would be ineffective for the extrusioncoating of welding flux.

The apparatus disclosed and claimed in copending application Ser. No.656,969, now U.S. Pat. No. (divided out of Ser. No. 552,655) providesfor the effective and uniform extrusion coating of a welding fluxcomposition composed of a mixture of liquid and solid flux materials, bysubstantially eliminating the tendency for the mixture to dilate duringextrusion and thereby preventing increases in extrusion pressure. Theextrusion apparatus comprises an extrusion nozzle, a flow guide with aconical passage in the center thereof adjacent to the noale, but spacedtherefrom for guiding welding flux composition therethrough to theextrusion nozzle, and a wire guide disposed within the center of theconical passage of the flow guide at a position spaced from the walls ofsaid passage for feeding welding rod or wire through the center of theconical passage and the noule. A piston and cylinder in closejuxtaposition to the flow guide, but spaced therefrom, provide thepressure for feeding the welding flux composition into and through thespace between the welding rod or wire and the walls of the flow guidepassage, to surround and enclose the rod or wire fed therethrough in asheath of welding flux composition. A hom having a vibrator elementattached thereto is connected to the apparatus for applying directly tothe flow guide sonic and/or ultrasonic wave vibration at a frequencywithin the range from about 5,000 to about 400,000 c.p.s. The spacedposition of the flow guide relative to the nozzle, the wire guide andthe welding flux composition pressure feeding means shield them fromsuch vibrations. The vibrating flow guide communicates the vibrations tothe welding flux composition passing therethrough so as to maintain thewelding flux composition uniform and inhibit its separation into liquidand solid components during extrusion, while maintaining a uniformextrusion of such composition at a uniform extrusion pressure. Thevibration of the particles of welding flux imparted thereto by the flowguide decreases the internal friction between the particles, maintainsthe uniformity of the mixture, and thereby prevents dilatancy andsqueezing out of the flux mixture during the extrusion operation, andeccentricity of the flux coating upon the welding electrode.

in accordance with the present invention, a method is provided (carryingforward the elected invention of Ser. No. 552,665) for the uniformextrusion coating of welding wire or rod with a welding fluxcomposition, in which high-frequency vibration is utilized to preventdilatancy, squeezing out and solidification of the flux mixture whensubjected to extrusion pressures.

Further, in accordance with this invention, another embodiment ofextrusion coating apparatus is provided that represents an improvementon the apparatus claimed in Ser. No. 656,969. The apparatus of thepresent invention provides an efficient means by which high-frequencyvibration is imparted to the particles of welding flux, to furtherinhibit the tendency of the welding flux mixture to dilate and solidifywithin the extrusion cylinder, thus ensuring a uniform concen triccoating of flux upon the welding electrode.

The extrusion coating method of this invention comprises, incombination, the steps of feeding welding rod or wire through the centerof an extrusion nozzle at a position spaced from the walls of thenozzle; pressure forcing welding flux composition into and through thespace between the welding rod or wire and the walls of the nozzle, tosurround and enclose the rod or wire fed therethrough in a sheath ofwelding flux composition; and applying vibration to the welding fluxcomposition prior to its passage through the extrusion nozzle, todecrease the internal friction between the particles of welding flux byimparting turbulent energy thereto, and to inhibit its separation intoliquid and solid components due to dilatancy by maintaining a uniformdispersion thereof, thus uniformly extruding such composition at auniform extrusion pressure.

Low-frequency mechanical or commercially available electrical vibratorsgive unsatisfactory results, since the pulses of energy applied to theflux particles are intermittent. Therefore, as previously disclosed,sonic and/or ultrasonic vibrating means having a frequency range ofapproximately 5,000 to 400,000 c.p.s. are employed for impartingvibration to the flux mixture. The higher the frequency of the vibrationwithin the range given, the better are the results obtained. Therefore,means for generating ultrasonic vibration with a frequency above 10,000c.p.s. up to approximately 400,000 c.p.s. is preferred. Such vibrationcan be converted to mechanical vibration at or near the nozzle member ofthe extrusion coating machine.

In the embodiments shown in copending U.S. Pat. application Ser. No.656,969, now U.S. Pat. No. 3,456,295, a sonic and/or ultrasonic vibratorelement is used in combination with a horn. The horn can be mounted ator near the nozzle member, with appropriate fastening means, so thatvibration can be imparted in a direction which is parallel with, orperpendicular to the direction of flux flow. The sonic and/or ultrasonicvibration can be applied as mechanical vibration of the extrusionnozzle, or the flow guide member adjacent to the extrusion nozzle, andis transmitted thereby to the flux particles themselves, causing theirmechanical vibration. The vibrational energy can also be transmitteddirectly from the horn to the flux particles in a direction which isoblique to the direction of particle flow prior to their compression bythe noule. In this manner, a greater amount of vibrational energy willbe absorbed by the particles. The resistance to coating will thus bedecreased, and in cooperation with the proper extrusion pressure, asmooth coating upon the welding rod or wire can be obtained. Whether thevibration is imparted first to a mechanical member or directly to theflux mixture, it is, of course, possible and desirable to provide aplurality of vibrators to increase the efficiency of the method. Thesecan be mounted in opposed or adjacent positions to each other.

The improved uniform extrusion coating apparatus of the presentinvention features another embodiment of means for imparting vibrationalenergy directly to the welding flux particles. The extrusion apparatuscomprising, in combination, an extrusion nozzle having a taperedentrance passage for guiding the welding flux composition into thenozzle; means disposed within the entrance passage for guiding weldingrod or wire through the center of the extrusion nozzle, at a positionspaced from the tapered walls of said entrance passage; means disposedin close juxtaposition to the entrance passage of the nozzle forpressure-forcing the welding flux composition into and through the spacebetween the welding rod or wire and the tapered walls of the entrancepassage, to surround and enclose the welding rod or wire in a sheath ofwelding flux composition; and means connected to the extrusion nozzlefor imparting directly to the particles of welding flux, prior to theextrusion thereof, sonic and/or ultrasonic vibration at a frequencywithin the range from about 5,000 to about 400,000 c.p.s. to maintain auniform dispersion of particles within the welding flux composition,inhibit its separation into liquid and solid components and decrease theinternal friction between flux particles during extrusion whileuniformly extruding such composition at a uniform extrusion pressure.

Preferably, the vibrating means employed in the extrusion apparatuscomprises a sonic and/or ultrasonic vibrator element and a hornconnected thereto to transmit the highfrequency vibrational wavesdirectly to the flux mixture in the tapered entrance passage of theextrusion nozzle. The vibration horns can be mounted on and within thebody of the extrusion nozzle so that the ends of the horns enter thetapered entrance passage of the nozzle at a position which is oblique tothe direction of flow. Although a horn mounted in either a parallel or aperpendicular position relative to the direction of flow will alsoimpart sufficient turbulent energy to the flux particles to ensureproper extrusion coating, it has been found that obliquely mounting thehorn yields the highest quality welding electrode, and vibration can bemost efficiently applied. The utilization of more than one vibrationhorn will ensure that the vibrational energy imparted to the weldingflux particles will be uniformly distributed within the mixture and notconcentrated in one area.

The vibration horns are shielded from the body of the extrusion nozzleto prevent the vibration of the entire apparatus. Applying the sonicand/or ultrasonic vibrational waves directly to the welding flux mixturein this manner ensures that only the flux particles will be vibrated,and further ensures that the extent of vibrational energy imparted tothe particles relative to the amount of vibrational energy generatedwill be greater than heretofore provided. Therefore, the operation ofthe extrusion apparatus is extremely efficient, and the flux coating ofthe electrode produced therefrom is completely uniform and concentric.

The invention will be further described with reference to theaccompanying drawings in which:

F IG. 1 is a longitudinal cross-sectional view of an apparatus for theuniform extrusion coating of welding flux composition in accordance withthe present invention.

FIG. 2 is a cross-sectional view of the extrusion apparatus taken alongthe lines 2-2 of FIG. 1 and looking in the direction of the arrows.

FIG. 3 is a graph representing the extrusion pressure and extrusion timerequired for coating a welding electrode with flux, with and without theapplication of vibration to the flux.

FIG. 4 is a graph comparing the required extrusion pressure for fluxcoating'of welding electrodes with and without vibrational waves appliedto the flux mixture.

The extrusion coating apparatus shown in FIG. l and FIG. 2 comprises apressure cylinder 10 and a conical extrusion head 8 which threadablyengages one end 13 of the cylinder 10,.the reentrant portion 15enclosing the end 13 in a pressuretight connection. A piston 9 isdisposed within the central bore 14 of the cylinder 10 to provide apositive pressure for feeding and extruding the flux mixture 7, confinedwithin the cylinder bore 14. The extrusion head 8 is provided with acentral bore 16 in which is fitted an extrusion nozzle 3 disposed in thecenter thereof, and an interior wall l2 which extends from cylinder 10to the central bore 16 and defines a passage which guides the fiow offlux material from the cylinder 10 to the nozzle 3. The diameter of thenozzle is approximately the diameter of the coated rod or wire, and islarger than the rod or wire by a distance approximately the depth of theflux coating thereon.

A welding wire or rod support member 11 is disposed within the bore 14of the cylinder 10 and a wire guide 5 is attached to the end of thesupport 11, so disposed within the tapered passage as to guide thewelding rod or wire 6 directly to the center of the extrusion nozzle 3as it is fed through the extrusion apparatus. Thus, the rod or wire canacquire a uniform concentric coating of flux material thereon as itpasses through the nozzle. The support ll also provides additionalguidance for the movement of piston 9 within cylinder 10, therebypreventing it from binding or jamming within the extruding apparatus.

The flux mixture 7 fills the annular space between the suppoit 11 andthe inside walls of the bore 14. On the pressure stroke of the piston 9,the flux material 7 is forced from the cylinder 10 into the taperedpassage, and subsequently through the nozzle 3, thereby being extrudedas a cylindrical coating upon the weld rod or wire 6 as shown in FIG. 2.

The vibrating means for imparting turbulent energy directly to theparticles of flux material to maintain a uniform dispersion thereof andto prevent dilatancy comprises a plurality of horns 2 each connected toa corresponding ultrasonic vibrator element 1. The horns 2 extendthrough tapered bores 17 in the head 8 to the interior wall 12, withtheir interior ends 18 mounted flush against the wall 12. Thepositioning of the interior ends 18 is ensured by a flange 4 on thehorns 2, which is bolted in place to the exterior of extrusion head 8.Each horn 2 is mounted obliquely to the direction of flow of the fluxmaterial, and their interior ends 18 are in direct contact with the fluxmixture 7. The horns 2 fit snugly within the bores 17 in head 8, so thatflux material under pressure cannot pass therebetween, yet they areshielded therefrom by means of a rubber sleeve 19 to inhibit vibrationof the head. The flange 4 is positioned at the node of the longitudinalvibration. Therefore, the horn vibrates freely, so that the amplitude ofthe portion which is in direct contact with the flux can be boosted toseveral times that of the vibrator element R. In this manner, arelatively small amount of energy is needed in order for the vibrator toimpart sufficient vibrational energy to the particles of flux materialto prevent dilatancy of the mixture upon its extrusion through thenozzle 3. By imparting the ultrasonic vibrations from the horn 2directly to the particles of flux, an extremely efficient and high speedextrusion operation can be maintained.

To carry out the method of the instant invention, a mass of flux mixture7 is deposited into the cylinder 10 and subjected to pressure bymovement of the piston 9 thereagainst. Simultaneously, sonic and/orultrasonic waves are transmitted from the vibrator 1 through the horn 2,to the flux mixture 7 located within the tapered passage 12. Theelectrode rod or wire 6 is then passed through guide 5. As the electrodeis passed through the nozzle 3, the flux mixture, which has beenvibrated by the horn 2, will be coated uniformly thereon. Thus, the fluxmixture is coated with decreased pressure and the coated productexhibits an improved smooth coating. By

use of the instant method and apparatus, production can be increasedfrom 60 to 95 percent above that of the conventional methods used in theprior art.

The following examples are set forth to illustrate the advantagesobtained by the utilization of the apparatus for the uniform extrusioncoating of welding flux materials, shown in FIGS. 1 and 2.

EXAMPLE 1 The materials and conditions employed were as follows:

Flux lime-type flux for welding rod Binder sodium silicate Core 4 mm.diameter by 400 mm. length Nozzle 6.3 mm. (inside diameter) Productionrate of the coated wire 400 meters per minute As shown in FIG. 3, thecoating operation was carried out without applying sonic wave vibrationto the flux mixture for the first one minute of operation. At the pointindicated by on," the sonic wave vibration was applied and the coatingoperation was continued until complete. The change in the requiredextrusion pressures after the application of the sonic vibration to thewelding flux mixture is clearly shown on the graph. The extrusionpressure was 600 kg./cm. prior to introduction of the sonic wavevibration, whereas the extrusion pressure decreased to 300 kg./cm.shortly after the vibration commenced. The decrease in extrusionpressure was due to the action of the sonic wave vibration upon theparticles of welding flux, whereby uniformity of the flux mixture wasmaintained and the internal friction between particles decreased.

EXAMPLE 2 This example is set forth to show the effect of the sonic wavevibration upon a welding flux material that is poor in fluidity and inwhich dilatancy and the resulting squeeze-out phenomenon are very likelyto occur. All other conditions employed are the same as those ofexample 1. As shown in curve B of FIG. 4, without vibration theextruding pressure gradually increases with the lapse of time, due todilatancy and the squeezing out of liquid rich flux from the center ofthe extrusion apparatus. The pressure as illustrated by curve B wasunstable and the coated surface of the welding rod thus attained wasfound to be scratchy and nonuniform. When the sonic wave vibration wasapplied to the welding flux mixture contained within the extrusionapparatus, the extrusion pressure was low and stable until the coatingoperation was completed, as illustrated by curve A. Moreover, the coatedsurface of the welding rod thus attained was found to be extremelyuniform and with few, if any, scratches.

Having regard to the foregoing disclosure, the following is claimed asthe inventive and patentable embodiments thereof.

1. A method for the substantially uniform extrusion coating through anextrusion nozzle of normally solid welding flux compositions composed ofa mixture of liquid and solid flux material, and having a tendency toundergo dilatancy with a resulting increase in extrusion pressure duringextrusion, comprising the steps of feeding welding rod or wire throughan extrusion nozzle at a position spaced from the walls of the nozzle;forcing welding flux composition under pressure into and through thespace between the welding rod or wire and the walls of the nozzle, tosurround and enclose the rod or wire fed therethrough in a sheath ofwelding flux composition; and applying sonic or ultrasonic vibration tothe welding flux composition but not to the extrusion nozzle or to therod or wire, directing the vibration to the portion of the fluxcomposition in proximity to and before it enters the extrusion nozzle,while extruding the composition through the extrusion nozzle, todecrease the internal friction between the particles of welding flux byimparting turbulent energy thereto, and to inhibit its separation intoliquid and solid corn nents by maintaining a uniform dispersion thereof,thus su stantrally uniformly extruding such composition andsubstantially uniformly coating the rod or wire therewith.

2. A method according to claim 1 in which sonic vibration having afrequency range of approximately 5,000 to 400,000 c.p.s. is applied tothe welding flux composition.

3. A method according to claim 1 in which ultrasonic vibration having afrequency range of approximately l0,000 to 400,000 c.p.s. is applied tothe welding flux composition.

4. A method according to claim 1 in which the vibration is applied to aflow guide member adjacent to the extrusion nozzle which in turn impartsthe vibration to the particles of flux composition.

5. A method according to claim 1 in which the vibration is imparteddirectly to the welding composition by the means creating the sonic orultrasonic vibrations to ensure that vibrational energy is imparted toall flux particles.

6. A method according to claim 4 in which the vibration is imparted tothe flow guide member in a direction which is parallel with thedirection of flux flow.

7. A method according to claim 4 in which the vibration is imparted tothe flow guide in a direction which is perpendicular to the direction offlux flow.

8. A method according to claim 1 in which the vibration is imparteddirectly to the welding flux composition in a direction which is obliquewith respect to the direction of flux flow.

2. A method according to claim 1 in which sonic vibration having afrequency range of approximately 5,000 to 400,000 c.p.s. is applIed tothe welding flux composition.
 3. A method according to claim 1 in whichultrasonic vibration having a frequency range of approximately 10,000 to400,000 c.p.s. is applied to the welding flux composition.
 4. A methodaccording to claim 1 in which the vibration is applied to a flow guidemember adjacent to the extrusion nozzle which in turn imparts thevibration to the particles of flux composition.
 5. A method according toclaim 1 in which the vibration is imparted directly to the weldingcomposition by the means creating the sonic or ultrasonic vibrations toensure that vibrational energy is imparted to all flux particles.
 6. Amethod according to claim 4 in which the vibration is imparted to theflow guide member in a direction which is parallel with the direction offlux flow.
 7. A method according to claim 4 in which the vibration isimparted to the flow guide in a direction which is perpendicular to thedirection of flux flow.
 8. A method according to claim 1 in which thevibration is imparted directly to the welding flux composition in adirection which is oblique with respect to the direction of flux flow.